This invention relates generally to a method and apparatus for delimbing and/or debarking elongated tree stems. More particularly it relates to a method and apparatus capable of delimbing a plurality of tree stems by motivating the stems through a delimbing station having a pair of offset vertically disposed flail members for knocking off the limbs and preferably for removing the bark substantially simultaneously.
In commercial forests today a substantial amount of relatively small timber is harvested and converted to many useful end products. In operations where tree thinning is performed to enhance the growth of the remaining trees, handling and processing systems are needed to efficiently and cost effectively handle the thinned trees. One of the common steps is the delimbing step where some means is used to remove the limbs and other foliage from the elongated stem. Flail means have been used in the past where flexible elements that are mounted on a rotating drum are caused to impact the stem where the limbs are attached. The force of the impact operates to break the limbs off the elongated stems.
One known flail delimbing apparatus has a rotating drum with chain segments mounted on the front end of a mobile prime mover. A collection of tree stems will be accumulated on the ground and the operator then drives the prime mover into a position where the moving chain segments are caused to impact the attached limbs and break them off. This apparatus leaves the debris and delimbed stems on the ground and another handling step is then necessary to dispose of the delimbed trees and resulting debris. This system also tends to leave short limb segments on the tree, at least on the sides of the trees that are facing the ground.
In the Swedish technical publication authored by T. Helgesson entitled "Flail Delimbing, A Bundle-Delimbing Method for Wood Removed in Thinning and Clearcutting Operations" (STFI Meddelande Series A, No. 472;4-21, 1978) there are disclosed several flail type machines for delimbing. One of the machines (depicted in FIG. 8 of the publication) has a horizontally mounted flail member at the back of a truck. The flail member is mounted on a carriage which moves back and forth over a plurality of tree stems laterally spaced on a deck.
Another machine is depicted in FIG. 7 of the publication and is a mobile delimbing apparatus having a pair of vertical axles on which chain segments are fastened. A gripper is used to pick up a bundle of trees and draws them through the rotating tools. The chains rotate against the direction of stem feed-through and, as the author states, the distance between the axles and the length of the chains is selected so that the chains touch each other when the axles rotate.
The present invention is an improvement in the type of flail delimbing machine just described having the vertical flail members. It was recognized that a plurality of elongated stems could be drawn through a vertical flail delimbing unit but adequate debris handling means should be provided and it was determined that an improved arrangement for the flail members with respect to the stem flow would result in improved delimbing and the possibility to also substantially debark the stems passing through the flail station.
Accordingly, from the foregoing, it is an object of the present invention to improve delimbing results in a vertical flail type delimbing machine.
Another object is to provide effective debris handling capability in the vertical flail delimber.
Yet another object is to provide a vertical flail machine that can debark elongated stems as well as the delimbing function.
Still a further object is to provide a vertical flail machine that is mobile and relatively inexpensive to manufacture and use.
These and other objects will become clear upon reading the specification to follow in conjunction with the attached drawings.